Method of and apparatus for recording data on optical recording medium

ABSTRACT

A method of and apparatus for recording data on an optical recording medium form a mark or a space by using a recording waveform having an erase pattern containing a multi-pulse. The method and the apparatus prevent distortion of the mark or the space and improve a mark shape such that a recording/reproducing characteristic of the optical recording medium is improved.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of prior U.S. application Ser. No.10/806,320, filed Mar. 23, 2004, currently pending, which is acontinuation of prior U.S. application Ser. No. 10/256,244, filed Sep.27, 2002, currently pending the disclosures of which are incorporatedherein by reference. This application claims the benefit of KoreanPatent Application Nos. 2001-61039, filed Sep. 29, 2001, and 2001-80541,filed Dec. 18, 2001, in the Korean Intellectual Property Office, andU.S. Provisional Application Nos. 60/327,305, filed Oct. 9, 2001, and60/373,377, filed Apr. 18, 2002, the disclosures of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of and apparatus for recordingdata on an optical recording medium, and more particularly, to a methodand apparatus in which digital data is recorded on an optical disc byforming a mark on the optical disc.

2. Description of the Related Art

Data are recorded on an optical disc which is one type of opticalrecording media, in a form of a mark on a track formed on the opticaldisc. A mark is formed as a pit in a read-only disc, such as a CompactDisc-Read Only Memory (CD-ROM) and a Digital Versatile Disc-Read OnlyMemory (DVD-ROM). In a recordable disc, such as a CD-R/RW and aDVD-R/RW/RAM, a phase-change film which is changed into a crystallinephase or an amorphous phase is formed on a recording layer, and a markis formed by a phase change of the phase-change film.

Methods of recording data can be divided into a mark edge recordingmethod and a mark position recording method. According to the markposition recording method, a signal of an amplitude of a detected RadioFrequency (RF) signal is changed from negative to positive or frompositive to negative at a location on which a mark is recorded.According to the mark edge recording method, the signal of the amplitudeof the detected RF signal is changed from negative to positive or frompositive to negative at both edges of the mark. Therefore, recording theedges of the mark is an important factor in improving quality of asignal reproduced from the optical disc.

However, in a disc on which the phase-change film is coated, it is shownthat a shape of a trailing edge of the mark recorded according to aprior art recording method changes according to a length of the mark oran interval between the marks, i.e., a space. That is, the trailing edgeof the mark is formed greater than a leading edge of the mark such thatrecording/reproducing characteristics of the disc are degraded. If arecording mark is relatively long, the recording/reproducingcharacteristics are more degraded.

FIGS. 1A-1E are reference diagrams of recording waveforms (a), (b), and(c) to record a Non Return to Zero Inverted (NRZI) data signal accordingto the prior art. The recording waveform (a) is used for recording theNRZI data signal on a DVD-RAM, the recording waveforms (b) and (c) arefor a DVD-RW. Here, T denotes a cycle of a reference clock. According tothe mark edge recording method, a high level of NRZI data is recorded asa mark and a low level of NRZI data is formed as a space. A portion ofthe recording waveform used in recording the mark is referred to as arecording pattern, and another portion of the recording waveform used informing the space (in erasing the mark) is referred to as an erasepattern. The prior art recording waveforms (a), (b) and (c) use amulti-pulse as the recording pattern, and a power of the erase patternis maintained constant in a predetermined DC level for an interval E asshown in FIG. 1E.

Since the DC level of the erase pattern included in the prior artrecording waveform is maintained constant for a predetermined period oftime, 0˜200° C. heat is continuously applied to a corresponding area toform the space. Therefore, if recording is repeatedly performed, a shapeof the mark is degraded and distorted such that therecording/reproducing characteristics of the optical disc are degraded.In particular, a development toward a high density and a high line speedfor recording more data on the optical disc makes the clock cycle Tshorter, and therefore a heat interference between pulses forming therecording waveform increases to cause more degradation of therecording/reproducing characteristics of the optical disc.

Meanwhile, in the prior art, the different recording waveforms are usedaccording to the kinds of the optical discs and specifications, such asDVD-RAM and DVD-RW, because characteristics of recording films of theoptical discs are different. In particular, due to the fact that thedifferent recording waveforms should be used for each kind of theoptical discs, a problem occurs in manufacturing a multi-drive which canrecord/reproduce all specifications of the optical discs because themulti-drive should accommodate a variety of the different recordingwaveforms. The problem causes an increase in cost.

SUMMARY OF THE INVENTION

To solve the above and/or other problems, it is an object of the presentinvention to provide a recording method and apparatus in whichdistortion of shapes of a leading edge and a trailing edge of a mark anddegradation of the mark caused by repeated recording operations can beprevented.

It is another object of the present invention to provide a recordingmethod and apparatus in which data is recorded by a recording waveformhaving an erase pattern which can improve a shape of a mark or a space.

It is yet another object of the present invention to provide a recordingmethod and apparatus in which data is recorded by a recording waveformwhich can be applied to a disc having a recording film with a variety ofcharacteristics.

Additional objects and advantages of the invention will be set forth inpart in the description which follows and, in part, will be obvious fromthe description, or may be learned by practice of the invention.

To accomplish the above and/or other objects of the present invention,there is provided a method of recording data on an optical recordingmedium. The method includes forming a mark or a space by using arecording waveform having an erase pattern containing a multi-pulse.

According to an aspect of the present invention, data is recordedaccording to a Run Length Limited (RLL) (2, 10) process in which 2 and10 are a minimum length and a maximum length of the mark or space,respectively, a first level of a predetermined Non Return to ZeroInverted (NRZI) data signal is recorded as the mark, and a second levelof the predetermined NRZI data signal is recorded as the space.

Also, to accomplish the above and/or other objects of the presentinvention, there is provided a method of recording data on the opticalrecording medium. The method includes generating a channel modulateddigital data (NRZI data) signal, generating the recording waveformhaving the erase pattern containing the multi-pulse and the recordingpattern, and forming the first level of the charnel modulate digitaldata signal as the mark and forming the second level of the channelmodulate digital data signal as the space by using the generatedrecording waveform.

According to an aspect of the present invention, the method is based onthe Run Length Limited (RLL) (2, 10) or RLL (1, 7) process in which 1and 7 are the minimum length and the maximum length of the mark orspace.

According to another aspect of the present invention, a power level of aleading pulse of the erase pattern is a low level of the multi-pulse andanother power level of a trailing pulse is a high level of themulti-pulse. Alternatively, the power level of the leading pulse of theerase pattern may be the high level of the multi-pulse, and the powerlevel of the trailing pulse may be the high level of the multi-pulse.The power level of the leading pulse of the erase pattern may be the lowlevel of the multi-pulse and the power level of the trailing pulse maybe the low level of the multi-pulse. The power level of the leadingpulse of the erase pattern may be the high level of the multi-pulse andthe power level of the trailing pulse may be the low level of themulti-pulse.

According to another aspect of the present invention, a ratio of aduration time of the high level and another duration time of the lowlevel of the multi-pulse is substantially 1:1, and the duration time ofthe high level is half a clock cycle.

It is possible that in the generating of the channel modulated digitaldata, the first level of the NRZI data signal is formed as the mark, andin the generating of the recording waveform, the second level of theNRZI data signal is formed as the space.

The recording waveform includes a cooling pulse, and the erase patternincludes a part of the cooling pulse. It is possible that if an endingtime of the cooling pulse is less than or greater than 0.5Ts from thetrailing edge of the NRZI data, the duration time of the leading pulseforming the erase pattern increases over 0.5Ts when T is a cycle of areference clock signal.

According to another aspect of the present invention, a unit pulseconstituting or included in the multi-pulse has a high level and a lowlevel that are adjusted by the duration time of the leading pulse of therecording pattern.

According to another aspect of the present invention, the recordingpattern has at least two power levels.

Also, to accomplish the above and/or other objects of the presentinvention, there is provided an apparatus for recording data on theoptical recording medium. The apparatus includes a recording waveformgenerating unit which generates the recording waveform having the erasepattern containing the multi-pulse and the recording pattern, and apickup unit which applies light to the optical recording mediumaccording to the generated recording waveform so that the mark or thespace is formed.

According to another aspect of the present invention, the apparatus alsoincludes a channel modulation unit which channel-modulates input datareceived from an outside source and outputs the generated NRZI datasignal to the recording waveform generating unit.

According to another aspect of the present invention, the pickup unitincludes a motor which rotates the optical recording medium, an opticalhead which applies a laser beam to the optical recording medium orreceives the laser beam reflected from the optical recording medium, aservo circuit which servo-controls the motor and the optical head, and alaser driving circuit which drives a laser device installed in theoptical head to generate the laser beam.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects and/or advantages of the present invention will becomemore apparent and more readily appreciated from the followingdescription of the preferred embodiments, taken in conjunction with theaccompanying drawings of which:

FIGS. 1A-1E are reference diagrams of recording waveforms according tothe prior art;

FIG. 2 is a block diagram of a recording apparatus according to anembodiment of the present invention;

FIG. 3 shows an example of an implementation of the recording apparatusof FIG. 2;

FIGS. 4A-4C show an example of a waveform generated by a recordingwaveform generating circuit of the recording apparatus of FIG. 3;

FIGS. 5A-5C show another example of a waveform generated by therecording waveform generating circuit of the recording apparatus of FIG.3;

FIGS. 6A through 6E are waveforms explaining four types of erasepatterns according to another embodiment of the present invention;

FIGS. 7A and 7D are other examples of the erase pattern of FIG. 6B;

FIGS. 8A through 10C are shapes of marks recorded in a simulation;

FIGS. 11A through 15 are graphs showing characteristics of a DVD-RAM;

FIGS. 16A through 20 are graphs showing characteristics of a DVD-RW; and

FIG. 21 is a flowchart showing a recording method according to anotherembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the present preferredembodiments of the present invention, examples of which are illustratedin the accompanying drawings, wherein like reference numerals refer tothe like elements throughout. The embodiments are described in order toexplain the present invention by referring to the figures.

FIG. 2 is a block diagram of a recording apparatus according to anembodiment of the present invention. Referring to FIG. 2, the recordingapparatus which forms a mark or a space on an optical recording medium(optical disc) 200, has a pickup unit 1, a recording waveform generatingcircuit 2, and a channel modulator 3.

The channel modulator 3 modulates input data which is input from anoutside source into a channel bit stream, such as a Non Return to ZeroInverted (NRZI) data signal. The recording waveform generating circuit 2receives the channel bit stream and generates a recording waveform torecord the received channel bit stream. The recording waveform generatedaccording to the embodiment of the present invention has an erasepattern having an erase multi-pulse. The recording waveform will beexplained later in detail. The pickup unit 1 applies light (a laserbeam) to the optical recording medium 200 according to the generatedrecording waveform so as to form the mark or the space.

FIG. 3 shows an example of an implementation of the recording apparatusof FIG. 2. The same blocks will be indicated by the same referencenumerals, and the same explanation will be omitted. Referring to FIG. 3,the recording apparatus includes the pickup unit 1, the recordingwaveform generating circuit 2, and the channel modulator 3. The pickupunit 1 has a motor 11 rotating the optical disc 200, an optical head 13receiving the light reflected from the optical disc 200, a servo circuit12 controlling the motor and the optical head, and a laser drivingcircuit 14 driving a laser device (not shown) installed in the opticalhead 13 to generate the light.

The channel modulator 3 modulates the input data into the channel bitstream and outputs the NRZI data signal. The recording waveformgenerating circuit 2 generates the recording waveform to record the NRZIdata signal and provides the recording waveform to the laser drivingcircuit 14. The laser driving circuit 14 forms the mark or the space bycontrolling the laser device in accordance with the received recordingwaveform.

FIGS. 4A-4C show an example of the recording waveforms generated by therecording waveform generating circuit 2. Referring to FIGS. 4A-4C, theNRZI data signal is changed from the input data according to amodulation method of the channel modulator 3. That is, if the modulationmethod is a Run Length Limited (RLL) (2, 10) series method. That is,according to an Eight to Fourteen Modulation (EFM) method, an Eight toFourteen Modulation plus (EFM+) method, a D (8-15) method, and a Dualmodulation method, a minimum length of the mark or the space is 3Ts anda maximum length of the mark or the space is 11Ts, where T is a cycle ofa clock signal as shown in FIG. 4A, The D (8-15) method is a modulationmethod disclosed in “Optical Disc Recording System of 25 GB Capacity”announced by Matsushita in Optical Data Storage (ODS) 2001. The Dualmodulation method is disclosed in Korean Patent Application No. 99-42032titled “An RLL code allocation method, modulation and demodulationmethod, and demodulation apparatus having improved DC controllingcapability,” filed by the present applicant on Sep. 30, 1999, andpublished on Nov. 25, 2000. If data is recorded using the RLL (1, 7)series method, the minimum length is 2Ts, and the maximum length is 8Ts.

When a high level of the NRZI data signal is formed as the mark and alow level of the NRZI data signal is formed as the space, the recordingwaveform includes a recording pattern to record a mark of a 7T length,an erase pattern to form a space of a 3T length, and another recordingpattern to record a mark of a 3T length as shown in FIG. 4B.

The recording pattern includes a pulse train, e.g., a multi-pulse. Also,the erase pattern is formed with another pulse train, e.g., anothermulti-pulse (erase multi-pulse) having an interval F as shown in FIG.4C. Tmp indicates a width of a pulse of the multi-pulse of the recordingpattern. Here, the multi-pulse indicates at least one pulse having thesame width and power. However, it is understood that the presentinvention is not limited thereto. That is, the width and the power ofeach pulse of the multi-pulse may vary. In the present embodiment, Tmpis 0.5Ts. Tlp indicates a width of a last pulse of the recordingpattern. Tcl indicates a width (duration time) of a cooling pulse. Thecooling pulse extends from the recording pattern to the erase pattern.Temp indicates a width of a pulse of the multi-pulse of the erasepattern. In the present embodiment, Temp is 0.5Ts. Tsfp indicates aperiod from a point where the NRZI data signal is transited from the lowlevel to the high level at a point (start point of a first pulse) whenthe first pulse forming the recording pattern starts. Tsfp is under aninfluence of a power level of the erase pattern. That is, as shown inFIG. 4C, if Tsfp is greater than 0.5Ts and the multi-pulse contained inthe erase pattern ends at low level Pb1, a next Tsfp starts from a highlevel Pb2 of the multi-pulse. Meanwhile, if Tsfp is less than 0.5Ts andthe multi-pulse contained in the erase pattern ends at a low level Pb1,the next Tsfp maintains the low level Pb1 of the multi-pulse.

FIGS. 5A-5C show another example of waveforms generated by the recordingwaveform generating circuit 2. Referring to FIG. 5B, when the high levelof the NRZI data signal is formed as the mark, and the low level isformed as the space, the recording waveform includes the recordingpattern to record a mark of a 7T length, the erase pattern to form aspace of a 5T length, and the recording pattern to record a mark of a 3Tlength.

The recording pattern includes the pulse train. Also, the erase patternis formed with the pulse train, e.g., the multi-pulse (erasemulti-pulse) having an interval G as shown in FIG. 5C. Tmp indicates thewidth of the multi-pulse forming the recording pattern. Here, themulti-pulse indicates at least one pulse having the same width andpower. However, it is understood that the present invention is notlimited thereto. That is, the width and the power of each pulse of themulti-pulse may vary. In the present embodiment, Tmp is 0.5Ts. Tlpindicates the width of the last pulse forming a recording pattern. Tclindicates the width (duration time) of the cooling pulse. The coolingpulse extends from the recording pattern to the erase pattern. Tempindicates the width of the erase multi-pulse constituting the erasepattern. In the present embodiment, Temp is 0.5Ts. Tsfp indicates aperiod from a point where the NRZI data is transited from the low levelto the high level at the point (start point of the first pulse) when thefirst pulse constituting the recording pattern starts. Tsfp isdetermined in response to the power level of the erase pattern. That is,as shown in FIG. 5C, if Tsfp is greater than 0.5Ts and the multi-pulsecontained in the erase pattern ends at low level Pb1, the next Tsfpstarts from the high level Pb2 of the multi-pulse. Meanwhile, if Tsfp isless than 0.5Ts and the multi-pulse contained in an erase pattern endsat the low level Pb1, the next Tsfp maintains the low level Pb1 of themulti-pulse.

FIGS. 6A through 6E are waveforms explaining four types of the erasepatterns according to another embodiment of the present invention.Referring to FIGS. 6A through 6E, the erase patterns are divided intothe four types: (a) LH, (b) HH, (c) HL, and (d) LL. Differences betweenthe power levels of the erase patterns are marked with circles so thatthe differences can be easily understood as shown in FIGS. 6B through6E.

First, the (a) LH indicates that a power of a leading pulse of the erasepattern is the same as the low level Pb1 of the following pulse of theerase multi-pulse, and when a last pulse of the erase multi-pulse of theerase pattern ends at the low level Pb1, the power level of thefollowing Tsfp is the same as the high level Pb2 of the erasemulti-pulse. The (b) HH indicates that the power of the leading pulseforming the erase pattern is the same as the high level Pb2 of thefollowing pulse of the erase multi-pulse, and when the last pulse of theerase multi-pulse of the erase pattern ends at the high level Pb2, thelevel of the following Tsfp continues to be the same high level Pb2 ofthe erase multi-pulse. The (c) HL indicates that the power of theleading pulse forming the erase pattern is the same as the high levelPb2 of the following pulse of the erase multi-pulse, and when the lastpulse of the erase multi-pulse of the erase pattern ends at the highlevel Pb2, the level of the following Tsfp is the same as the low levelPb1 of the erase multi-pulse. Finally, the (d) LL indicates that thepower of the leading pulse forming the erase pattern is the same as thelow level Pb1 of the following pulse of the erase multi-pulse, and whenthe last pulse of the erase multi-pulse of the erase pattern ends at thelow level Pb1, the level of the following Tspf continues to be the samelow level Pb1 of the erase multi-pulse.

FIGS. 7A and 7D are other examples LH2 and LH3 of LH of FIG. 6B.Referring to FIGS. 7A and 7D, the (e) LH2 is the same as (a) LH of FIG.6B, except that Temp1, a duration time of the high level Pb2 of themulti-pulse forming a cycle, is 0.7Ts and Temp2, a duration time of thelow level Pb1 of the multi-pulse, is 0.3Ts. Also, the (f) LH3 is thesame as (a) LH of FIG. 6B, except that the duration time of the highlevel Pb2 or the low level Pb1 of the multi-pulse is 1.0T. Here, a ratioof Temp1 and Temp2, that is, the ratio of the duration time of the highlevel Pb2 and that of the low level Pb1 of the multi-pulse forming acycle can be changed as m:n in a variety of ways. (Here, m and n areintegers.) Thus, the recording waveform according to the presentinvention has the erase pattern containing the multi-pulse (erasemulti-pulse) of which power is the high level Pb2 or the low level Pb1,and therefore distortion of the trailing edge of the mark is preventedand the reproducing characteristic of the optical disc is improved. Inparticular, in the recording waveforms shown in the embodimentsdescribed above, the duration time of the high level Pb2 and the lowlevel Pb1 of the multi-pulse is adjusted within a range between 0.25Tsand 0.75Ts for a clock cycle T, and a duration time appropriate to heatcharacteristic of the optical disc 200 is selected. Therefore, thereproducing characteristic of the optical disc is more improved.

Meanwhile, information on the four types of the erase patterns (typeinformation) may be recorded in a lead-in area of a recordable disc(optical disc) or may be included in a wobble signal as one of headerinformation items. In this case, when data are recorded, the recordingapparatus reads type information from the lead-in area or from thewobble signal to form the mark or the space by generating acorresponding recording waveform.

In addition, the four types of the erase patterns may be used as asymbol indicating multiple times speed of the disc or the kind of themark when data is recorded and reproduced. For example, the erasepattern may indicate information of “the speed of a disc using LH typeerase pattern is 20-multiple times speed.”

In order to test an effect of the present invention, shapes of the markrecorded in a simulation were observed. A structure used in thesimulation is shown in table 1. The disc used in the simulation has a4-layered film structure.

TABLE 1 Dielectric Recording Dielectric Reflecting Substrate film filmfilm film Material PC ZnS—SiO₂ Sb—Te ZnS—SiO₂ Ag alloy eutectic Thick-0.6 mm 128 nm 14 nm 16 nm 30 nm ness

Each condition of the simulations includes a wavelength of 405 nm, anumeral aperture (NA) of 0.65, and a linear velocity of 6 m/s. In orderto observe the shape of the mark, after a recording mark of 8T isrecorded, a next recording mark of 8T is recorded by overlapping 4T ofthe previous recording mark of 8T. FIGS. 8A through 10C show comparisonresults between the mark shapes when the prior art recording waveformwas used and the mark shapes when the recording waveform according tothe present invention was used. FIG. 8A, shows a mark (a) formed by thesimulation, FIG. 8B shows a mark (b) formed on the mark (a) by arecording waveform according to the present invention, and FIG. 8C showsa mark (c) formed on the mark (a) by the prior art recording waveform.Likewise, FIG. 9A shows a mark (d) formed by the simulation, FIG. 9Bshows a mark (e) formed by the recording waveform having the erasepattern according to the present invention, and FIG. 9C shows a mark (f)formed by the recording waveform having the prior art DC erase pattern.FIG. 10A shows a mark (g) formed by the simulation, FIG. 10B shows aresult of erasing the mark (g) by the erase pattern according to thepresent invention, and FIG. 10C shows a result of erasing the mark (g)by the prior art DC erase pattern.

Table 2 shows parameters of thin films of the optical disc used inanother simulation for interpreting heat.

TABLE 2 λ = 405 nm Material n K C(J/cm³K) k(W/cmK) ZnS—SiO₂ 2.300 0.0002.055 0.0058 Sb—Te eutectic 1.650 3.150 1.285 0.0060 (Crystal) Sb—Teeutectic 2.900 2.950 1.285 0.0060 (Amorphous) Ag alloy 0.170 2.070 2.4500.2000

Referring again to simulation results of FIGS. 8A through 10C, it isshown that the trailing edge of the mark (b) formed by the recordingwaveform having the erase pattern according to the present invention asshown in FIG. 8B is better than the trailing edge of the mark (c) formedby the recording waveform having the prior art DC erase pattern of theprior art method as shown in FIG. 8C. Like the trailing edges, the shapeof the leading edge of the mark is better when the erase patternaccording to the present invention as shown in FIG. 9B. The results ofthe simulation show that the shape of the mark when the recordingwaveform having the erase pattern formed with the erase multi-pulse isused, is improved compared with the prior art. By adjusting the shape,width, and power level of the erase multi-pulse, distortion of the shapeof the mark can be more reduced.

In order to experimentally verify the effect of the present invention,parameters needed in obtaining the recording waveforms shown in FIGS. 4Athrough 5C, that is, the duration time and the power level, wereobtained from a 4.7 GB DVD-RAM disc and a 4.7 GB DVD-RW disc using a DVDevaluator of which the laser wavelength is 650 nm and the NA is 0.60.Then, characteristics of repetitive recording/reproducing the NRZI datasignal according to the present invention were compared with the priorart method.

FIGS. 11A through 15 are graphs showing the characteristics of theDVD-RAM. FIGS. 11A through 13B show features of power and time ofrecording the NRZI data signal using the recording waveform with the DCerase pattern of the prior art, and FIGS. 14A, 14B, and 15 show improvedfeatures of recording the NRZI data signal using the recording waveformof the present invention. FIGS. 11A and 11B show jitter characteristicswith respect to recording power and erase power, respectively, for theleading edge, trailing edge, and both edges of the mark in the prior artDC erase. Based on the jitter characteristics, 14.5 mW recording powerand 6 mW erase power were selected for experiments.

FIGS. 12A through 13B show the measured results in the prior art DCerase. Referring to FIGS. 12A-12G and FIGS. 13A and 13B, the mostpreferable jitter characteristics are shown when Tsfp=0.5Ts and whenTsfp=0.4Ts. Tcl didn't affect the jitter characteristics, and Tlp wasgood when the cycle is 0.7Ts.

Based on the parameters experimentally obtained in this way, the markwas formed with the recording waveform having the four types of erasepatterns described above, and the characteristics of the formed markwere measured as the following.

FIGS. 14A and 14B show the jitter characteristics of the four typesaccording to the present invention shown in FIG. 6. Referring to FIGS.14A and 14B, it can be inferred that jitter characteristic is good whenthe NRZI data signal is recorded using the recording waveform with theerase pattern, i.e., any one of the four types of the erase patternshown in FIGS. 6A-6E, of the present invention. Especially, referring toFIG. 14A, it is shown that the LH type is the best among the four types.Referring to FIG. 14B, when the erase pattern formed with the erasemulti-pulse according to the present invention is used in erasing themark, the jitter characteristics of ΔPb (Pb2-Pb1), which is a differencebetween the high level and the low level of the erase multi-pulse, isshown. It is shown that up to 5 mWs there is no big difference.

FIG. 15 shows the jitter characteristics of the results of repetitiverecording/reproducing using the recording waveform having the erasepattern according to the present invention compared with the prior art.Referring to FIG. 15, it is easily understood that when the mark iserased using the erase multi-pulse according to the present invention,the result is good, especially in the repetitive recordingcharacteristics aspect.

FIGS. 16A through 20 are graphs showing characteristics of the DVD-RW.FIGS. 16A through 18B show features of power and time of recording theNRZI data signal using the recording waveform with the DC erase patternof the prior art, and FIGS. 19A through 20 show improved features ofrecording the NRZI data signal using the recording waveform of thepresent invention.

FIGS. 16A and 16B show jitter characteristics with respect to recordingpower and erase power, respectively, for the leading edge, trailingedge, and both edges of the mark in the prior art DC erase. Based onFIGS. 16A and 16B, 14.0 mW recording power and 6 mW erase power wereselected.

FIGS. 17A through 18B show the measured results in the prior art DCerase. Referring to FIGS. 17A through 18B, the most preferable jittercharacteristics are shown when Tsfp=0.3Ts and when Tsfp=0.05Ts. Tcl wasgood in 0.55Ts, and Tlp was good in 1.0T and 1.1Ts.

Based on the parameters experimentally obtained in this way, the markwas formed with the recording waveform having the four types of erasepatterns described above, and the reproducing characteristics of theformed mark were measured as the following.

FIGS. 19A and 19B show the jitter characteristics of the four typesshown in FIGS. 6B through 6E. Referring to FIG. 19A, it is shown thatthe LH type is the best among the four types. When the erase patternformed with the erase multi-pulse according to the present invention isused in erasing the mark, the jitter characteristics of ΔPb(Pb2-Pb1)which is the difference between the high level and the low level of theerase multi-pulse is shown. Since the characteristics are suddenlydegraded from 3 mW, 1 mW was selected as a condition for the repetitiverecording/reproducing experiment.

FIG. 20 shows the jitter characteristics of the results of repetitiverecording/reproducing the NRZI data signal using the recording pulsehaving the erase pattern according to the present invention. Referringto FIG. 20, it is easily understood that when the mark is erased usingthe erase multi-pulse according to the present invention, the result isgood, especially in the repetitive recording characteristics aspect.However, the jitter characteristics were suddenly degraded from 2,000times. Therefore, it is shown that the pulse erase method according tothe present invention is advantageous up to 1,000 times repetitiverecording that is guaranteed in the normal DVD-RW.

Meanwhile, the above experiments followed the DVD formats and thereforethe EFM+ modulation method was used. However, if any of other modulationmethods that are normally used, for example, the RLL (1, 7) method, theD (8-15) method, and the Dual modulation method, is used, the resultwill be the same.

A recording method according to another embodiment of the presentinvention based on the structure described above will now be explained.

FIG. 21 is a flowchart showing the recording method. Referring to FIG.21, the recording apparatus receives data from the outside source,modulates the data, and generates the NRZI data signal in operation1801. Then, the recording apparatus generates the recording waveformhaving the erase pattern containing the erase multi-pulse in operation1802. Using the generated recording waveform, the mark or the space isformed on the optical disc 200 in operation 1803.

As described above, according the present invention, the method of andapparatus for recording data using the recording waveform preventsdistortion of the shape of the mark occurring due to heat interferenceand heat accumulation when data is recorded, and improves the shape ofthe mark so that the characteristics of recording/reproducing of thedata are improved.

Although a few preferred embodiments of the present invention have beenshown and described, it would be appreciated by those skilled in the artthat changes may be made in this embodiment without departing from theprinciples and sprit of the invention, the scope of which is defined inthe claims and their equivalents.

1. An apparatus for recording data to an optical recording medium,comprising a recording waveform generating unit generating a recordingwaveform which includes a first multi-pulse corresponding to a firstlevel of input data, a second multi-pulse corresponding to a secondlevel of the input data, and a cooling pulse, the first multi-pulsefollowing the second multi-pulse, and the second multi-pulse having aleading pulse, second low power pulses having a low power level andsecond high power pulses having a high power level; and a pickup unit todrive a laser to generate a laser beam according to the generatedrecording waveform and an optical head to focus the laser beam on theoptical recording medium to create spaces and marks using the generatedrecording waveform, wherein: the leading pulse is set to the low powerlevel and a power level of a period between an end of the secondmulti-pulse and a start of the first multi-pulse is set to the highpower level, and the cooling pulse extends from an end of another firstmulti-pulse preceding the second multi-pulse to the leading pulse andhas a cooling power level that is less than the low power level.
 2. Theapparatus of claim 1, wherein the input data comprises NRZI data havinga high potential and a low potential each representing one of the firstlevel and the second level.
 3. The apparatus of claim 1, wherein thefirst state is a mark, and the second state is a space.
 4. The apparatusof claim 1, wherein the first multi-pulse is a recording pattern to forma mark, and the second multi-pulse is an erase pattern to form a space.5. The apparatus of claim 1, wherein the cooling pulse begins while therecording waveform is at the first level of the input data and endswhile the recording waveform is at the second level of the input data.6. The apparatus of claim 1, further comprising: a servo unit rotatingthe optical recording medium according to one of the first multi-pulseand the second multi-pulse during forming the first state and the secondstate.
 7. The apparatus of claim 6, wherein the servo unit controls arotation speed of the optical recording medium in accordance with one ofthe leading pulse and an ending pulse of the second multi-pulse.
 8. Theapparatus of claim 1, wherein the recording waveform generating unitgenerates information data representing a characteristic of the secondmulti-pulse using data detected from a wobble signal on the opticalstorage medium.
 9. The apparatus of claim 8, further comprising: a servounit rotating the optical recording medium in accordance with theinformation data.
 10. The apparatus of claim 9, further comprising: aservo unit receiving the information data read from the opticalrecording medium and rotating the optical recording medium at a speedcorresponding to the received information data.
 11. The apparatus ofclaim 8, wherein the optical recording medium comprises a lead-in-area,and the information data is recorded in the lead-in-area of the opticalrecording medium.
 12. The apparatus of claim 8, further comprising: aservo unit rotating the optical recording medium at a first speed,receiving the information data from the optical recording medium, androtating the optical recording medium at a second speed according to thereceived information data.
 13. An apparatus for recording data to anoptical recording medium, comprising a recording waveform generatingunit generating a recording waveform which includes a first multi-pulsecorresponding to a first level of input data and a second multi-pulsecorresponding to a second level of the input data, the secondmulti-pulse having a leading pulse, second low power pulses having a lowpower level and second high power pulses having a high power level; anda pickup unit to drive a laser to generate a laser beam according to thegenerated recording waveform and an optical head to focus the laser beamon the optical recording medium to create spaces and marks using thegenerated recording waveform, wherein: the leading pulse is set to thelow power level and a power level of a period between an end of thesecond multi-pulse and a start of the first multi-pulse is set to thehigh power level, and the first multi-pulse has corresponding first highpower pulses having a first high power level greater than the high powerlevel of the second multi-pulse and first low power pulses having afirst low power level less than the low power level of the secondmulti-pulse.
 14. The apparatus of claim 13, wherein the second highlevel of the second pulses is smaller than the first high level of thefirst pulses.
 15. The apparatus of claim 13, wherein the recordingwaveform generating unit selected between the low and high power levelsto set the power level of the period to be the high power level due to alast one of the pulses of the second multi-pulse.
 16. The apparatus ofclaim 13, wherein each pulse in the first multi-pulse has a first dutycycle, and each pulse in the second multi-pulse has a second duty cycle.17. The apparatus of claim 16, wherein the second duty cycle comprises:a duration time of the high power level and/or another duration time ofthe low power level is in a range between 0.25T and 0.75T, where T is acycle of a reference clock.
 18. An apparatus for recording data to anoptical recording medium, comprising a recording waveform generatingunit generating a recording waveform which comprises a first multi-pulsecorresponding to the first level of input data, a second multi-pulsecorresponding to the second level of the input data, and a cooling pulseconcatenating the second multi-pulse and another first multi-pulsepreceding the second multi-pulse, the first multi-pulse following thesecond multi-pulse, and the second multi-pulse having a leading pulse,high power pulses having a high power level and low power pulses havinga low power level greater than a cooling power level of the coolingpulse; and a pickup unit to drive a laser to generate a laser beamaccording to the generated recording waveform and an optical head tofocus the laser beam on the optical recording medium to create spacesand marks using the generated recording waveform, wherein the leadingpulse of the second multi-pulse is set to the low power level and apower of a period between an end of the second multi-pulse and the firstmulti-pulse is set to the high level.
 19. An apparatus for recordingdata to an optical recording medium, comprising a recording waveformgenerating unit generating a recording waveform which comprises a firstmulti-pulse corresponding to the first level of input data, a secondmulti-pulse corresponding to the second level of the input data, and acooling pulse concatenating the second multi-pulse and another firstmulti-pulse preceding the second multi-pulse, the first multi-pulsefollowing the second multi-pulse, and the second multi-pulse having aleading pulse, high power pulses having a high power level and low powerpulses having a low power level greater than a cooling power level ofthe cooling pulse; and a pickup unit to drive a laser to generate alaser beam according to the generated recording waveform and an opticalhead to focus the laser beam on the optical recording medium to createspaces and marks using the generated recording waveform, wherein theleading pulse of the second multi-pulse is set to the high power leveland a power level of a period between an end of the second multi-pulseand the first multi-pulse is set to the high power level.
 20. Anapparatus for recording data to an optical recording medium, comprisinga recording waveform generating unit generating a recording waveformwhich comprises a first multi-pulse corresponding to the first level ofinput data, a second multi-pulse corresponding to the second level ofthe input data, and a cooling pulse concatenating the second multi-pulseand another first multi-pulse preceding the second multi-pulse, thefirst multi-pulse following the second multi-pulse, and the secondmulti-pulse having a leading pulse, high power pulses having a highpower level and low power pulses having a low power level greater than acooling power level of the cooling pulse; and a pickup unit to drive alaser to generate a laser beam according to the generated recordingwaveform and an optical head to focus the laser beam on the opticalrecording medium to create spaces and marks using the generatedrecording waveform, wherein the leading pulse of the second multi-pulseis set to the low power level and a power level of a period between anend of the second multi-pulse and the first multi-pulse is set to thelow power level.
 21. An apparatus for recording data to an opticalrecording medium, comprising a recording waveform generating unitgenerating a recording waveform which includes a first multi-pulsecorresponding to the first level of input data, a second multi-pulsecorresponding to the second level of the input data, and a cooling pulseconcatenating the second multi-pulse and another first multi-pulsepreceding the second multi-pulse, the first multi-pulse following thesecond multi-pulse, and the second multi-pulse having a leading pulse,high power pulses having a high power level and low power pulses havinga low power level greater than a cooling power level of the coolingpulse; and a pickup unit to drive a laser to generate a laser beamaccording to the generated recording waveform and an optical head tofocus the laser beam on the optical recording medium to create spacesand marks using the generated recording waveform, wherein the leadingpulse of the second multi-pulse has a same power level as a power levelof a period between an end of the second multi-pulse and the firstmulti-pulse.